1. Field of the Invention
The present invention relates to a shrink film comprising a non-crystalline ethylene-alkenyl aromatic hydrocarbon copolymer.
2. Description of the Related Arts
As labels for plastic or glass containers, shrink films which are easily torn off from the containers, have been frequently used due to scrapping after used or recycled. As a raw material resin for the shrink film, a polyvinyl chloride resin, styrene-butadiene block copolymer resin, polyethylene terephthalate(PET) resin, polyolefin resin or the like has been used. Particularly, it is required that the shrink film has a low temperature shrinking property, which is capable of shrink-wrapping at a temperature of 100xc2x0 C. or lower, preferably round 80xc2x0 C. from a viewpoint of protection of the contents. When the degree of shrinking at normal temperature(herein-after, referred to as xe2x80x9cnatural shrinkagexe2x80x9d) of the shrink film is large, there are problems that the film can not be applied to a shrinking machine or the printed pattern thereon is deformed because of the natural shrinkage during a storage of the film, and the commercial value is lost. Therefore, a film of a small natural shrinkage is required.
A polyvinyl chloride resin has been much used for use of shrink film because of small natural shrinkage and good low temperature shrinking property. However, from a recent upsurge of environmental consciousness, a change to non-chlorine polymer materials for one-way containers, has been required. As the non-chlorine polymer, a styrene-butadiene block copolymer or a polyethylene terephthalate resin has been used. However, the natural shrinkage is large because the styrene-butadiene block copolymer has a glass transition point below 0xc2x0 C., and therefore the cold storage in summer time is necessary. Accordingly, there is a problem in industrial. On the other hand, when the bottle is made of the polyethylene terephthalate resin (called as xe2x80x9cPET bottlexe2x80x9d), the separation into the bottle(plain) and the label (printed) is required for recycling. But, the separation is difficult or a special separation machine is necessary because the specific gravity thereof is the same each other. Therefore, this resin also has a problem in industrial.
Further, a shrink film of an olefin resin has been developed, but because the shrinkage ratio is small at a temperature during shrink-wrapping, for example, at 80xc2x0 C. and the rigidity is low, the label can not be sufficiently adhered to a container. Therefore, there is also a problem such as reduction of the commercial value.
As mentioned above, although various resin have been used as the shrink film and studied for development, no film to be satisfied is actually obtained.
An object of the present invention is to provide a shrink film having a transparency, a low temperature shrinking property, a high shrinkage ratio, a small natural shrinkage, composed of a non-chlorine resin.
The present invention relates to a shrink film comprising a non-crystalline ethylene-alkenyl aromatic hydrocarbon copolymer.